Many modern electronic instruments collect and display giga-samples of some measured quantity. Displaying this data for analysis by a user presents challenges. The amount of data is too large to view on a single display with a resolution that allows small features to be seen accurately. Accordingly, the display on the instrument is utilized as a window that views a portion of the stored data array at a time.
For the purposes of this discussion, a data array is defined to be an ordered set of measurements in which each member of the array is characterized by a value and an index in the array. A plot of the data typically involves plotting the data values as a function of the index with the index translated to time or some other variable. For example, in an oscilloscope, the data array is typically a series of amplitude measurements with the index corresponding to the time at which the measurement was made.
A display window is defined to be a plot of the data array values for index values from starting value through some ending value. Typically, the vertical axis of the plot corresponds to the data values, and the horizontal axis corresponds to the corresponding index values. The starting value is referred to as the offset of the window. The magnification of the window is defined to be the length of the display window in pixels on the display screen divided by the difference between the ending value of the index and the beginning value.
Increasing the magnification is often referred to as zooming in, as the data values are displayed with greater separation between the values. The user typically selects a zoom level that allows the user to search for features of interest in the data. At this stage of the examination, the user typically selects a zoom level that allows the user to view the maximum amount of data in the window while still being able to detect features of interest that occur in the window. However, the magnification is typically insufficient to view the details of a feature found in such a scan of the data. To view a feature of interest, the user must “zoom in” on the feature of interest. This operation typically requires the user to reposition the window such that the feature is within the window and then increase the magnification to view the details of the feature. If the feature of interest is not accurately centered in the window, the zoom operation can result in the feature of interest being moved to a location outside the window. The user must then reposition the window at the new zoom level, and possibly, again change the zoom to provide the desired level of detail. When the instrument has a very large data set, zooming in on a feature of interest often requires multiple passes. This procedure is time consuming, and often, frustrating.